Problem: Add.
Explanation: There are many ways to solve this problem. Let's see two ways we can solve it. Place value table Let's line up the numbers by their decimal places. Tens Ones $.$ Tenths $7$ ${8}$ $.$ ${7}$ $7$ $.$ ${0}$ Because $7$ is a whole number, we can add a decimal point and a $0$ behind to make the columns align. Now, let's add each place value column. Tens Ones $.$ Tenths $\overset{1}{{7}}$ ${8}$ $.$ ${7}$ $+$ ${7}$ $.$ ${0}$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $8$ $5$ $.$ $7$ Decomposing the numbers We can group the whole numbers together and the decimals together. $\begin{aligned} &({78} + 7) + {0.7}\\\\ &=85 + {0.7}\\\\ &=85.7 \end{aligned}$ $85.7 = 78.7 + 7$